Methods of making incandescent lamps

ABSTRACT

A method of making an incandescent lamp comprises passing a filament for the lamp and a filament support through an opening in a bulb so that conductors from the filament pass out through the opening. An exhaust tube is then placed partially inside the bulb through the opening with the conductors passing between the tube and the edge of the wall of the bulb surrounding the opening. The exhaust tube is then sealed to the bulb and the interior of the bulb subjected to a vacuum. The exhaust tube is then sealed and a cap is threaded over the exhaust tube on to the sealed joint between the exhaust tube and the bulb. The cap has two contact members for electrical connection to the conductors.

United States Patent 2 15] 3,685,881 Rochet 1. Aug. 22, 1972 15 1 METHODS OF MAKING 2,946,641 7/1960 Wisner ..316/19 INCANDESCENT LAMPS Primary Examiner-John F. Campbell [72] Inventor gg g gg z zfi z Sad] a Assistant Examiner-Richard Bernard Lazarus Attorney-Robert E. Burns and Emmanuel .l. Lobato [22] Filed: July 7, 1970 Appl. No.: 52,923

[ ABSTRACT A method of making an incandescent lamp comprises passing a filament for the lamp and a filament supportthrough an opening in a bulb so that conductors from the filament pass out through the opening. An exhaust tube is then placed partially inside the bulb through the opening with the conductors passing between the tube and the edge of the wall of the bulb surrounding the opening. The exhaust tube is then sealed to the bulb and the interior of the bulb subjected to a vacuum. The exhaust tube is then sealed and a cap is threaded over the exhaust tube on to the sealed joint between the exhaust tube and the bulb. The cap has two contact members for electrical connection to the conductors.

1 Claim, 7 Drawing Figures METHODS OF MAKING INCANDESCENT LAMPS BACKGROUND OF THE INVENTION This invention relates to methods of manufacturing incandescent lamps having a filament within an evacuated bulb.

In known methods difiiculties are often encountered AIMS OF THE INVENTION An object of the present invention is to provide a method which substantially minimises the above mentioned disadvantages.

According to the present invention, a method of manufacturing an incandescent lamp including a bulb, a filament positioned within the bulb, and a cap positioned over at least a portion of the bulb and having two electrical contacts, comprises the steps of passing the filament and a filament support into the bulb through an opening in the bulb, electrical conductors from the filament emerging from the opening in the bulb, placing an exhaust tube partially inside the bulb through the opening, the conductors passing between the exhaust tube and the bulb, heat sealing the exhaust tube to the bulb, subjecting the interior of the bulb to a vacuum, hermetically sealing the exhaust tube and threading the cap over the exhaust tube for connection to the sealed joint between the exhaust tube and the bulb, the cap having two electrical contacts for electrical connection to the conductors.

DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described, by way of example, reference being made to the Figures of the accompanying drawings in which FIG. 1 is a cross-section of a bulb, and of an exhaust tube ready to be placed in the bulb;

FIG. 2 is a cross-section of the bulb and of the exhaust tube, the latter having been placed in the upper part of the bulb;

FIG. 3 is an elevation of the bulb and the exhaust tube after heat sealing;

FIG. 4 is a top plan view of the exhaust tube after heat sealing;

FIG. 5 is an elevation of the bulb and the exhaust tube after the exhaust tube has been heated then drawn out for heat sealing the tube;

FIG. 6 is an elevation of the bulb after sealing and separation of the exhaust tube; and

FIG. 7 is an elevation of a lamp.

DESCRIPTION OF A PREFERRED EMBODIMENT As shown in FIG. 1, a glass bulb has a drawn neck 2 at an open end. The first operation of the method according to the invention consists of inserting an electrical unit comprising a filament 3, its support 4, made, for example, of glass and two conductors 5 and 6 for the current to the filament, through the neck 2. The ends of these conductors emerge from the bulb and are bent outwards at the level of the neck.

Advantageously, the bulb 1 is placed head downwards so that, during the first operation, the electrical unit enters the bulb 1 under gravity. In a second operation, one end of an exhaust tube 7, i.e. a glass tube intended to form the vacuum, is inserted through the neck 2 to a length equal to the length of the neck 2. The external diameter of the exhaust tube 7 is slightly smaller than the interior diameter of the neck so that sufficient clearance exists for the exhaust tube 7 to be inserted despite the presence of the conductors 5 and 6 which are situated between the exhaust tube 7 and the neck 2.

In a third operation (FIG. 3), the group of parts composed of the neck 2, the end of the exhaust tube 7 and the parts of the conductors 5 and 6 outside the bulb 1 are gripped by a device (not shown) which both heats the glass of the neck 2 and exerts a closing pressure. During this operation, a needle of tungsten, a metal with a very high fusion point, is fed through the exhaust tube 7, to prevent the inner surface of the exhaust tube being deformed under the effect of the heat. The neck 2 and the end of the exhaust tube 7 are thus heat sealed and the mark left by the closing pressure device can be, for example, of a square shape (FIG. 4).

After cooling, the tungsten needles is withdrawn and a vacuum is produced inside the bulb, through exhaust tube 7. After this operation is finished, the exhaust tube 7 is hermetically cut and sealed by heat as indicated by arrows A. At the same time, the exhaust tube 7 is drawn out, for example, by the weight of the bulb 1 and its contents. After this cutting operation, the lamp is in the shape of a drop glass 8 (as seen in FIG. 6) from which the conductors 5 and 6 emerge.

In the last operation of the'method, a metal cap 9 is threaded over the end of the bulb 2 and two electrical contacts in the form of studs 10 and 11 for electrical connection are made thereon. For this purpose, the cap 9 has, at its rear end, a drilled insulating ring 12 through which the conductor 6 is brought out, enabling contact 1 l to be soldered.

As for contact 10, this can be made, for example, by leading conductor 5 out between the cap and the wall of the bulb, or by leading this conductor through a hole made in the front part of the cap. The cap itself can be attached to the rear part of the bulb by cold or hot gluemg.

Obviously, instead of the contact studs being arranged as previously described, two contact studs can be placed, for example, at the rear part of the cap; pins can also be introduced.

From the foregoing, it can be seen that the embodiment described has numerous advantages, notably the particularly simple way in which lamps can be produced.

It is understood that the invention is not limited to the method of application nor to the embodiment which has been mentioned; different variations can be envisaged without, thereby departing from the scope of the invention as claimed.

What is claimed is:

l. A method of manufacturing an incandescent lamp including a bulb, a filament positioned within the bulb and a cap positioned over at least a portion of the bulb and having two electrical contacts, the method comprising the steps of passing the filament and a filament support into the bulb through an opening in the bulb electrical conductors from the filament emerge from hermetically sealing the exhaust tube and threading the cap over the exhaust tube for connection to the sealed joint between the exhaust tube and the bulb, the cap having two electrical contacts for electrical connection to the conductors.

l I I 

1. A method of manufacturing an incandescent lamp including a bulb, a filament positioned within the bulb and a cap positioned over at least a portion of the bulb and having two electrical contacts, the method comprising the steps of passing the filament and a filament support into the bulb through an opening in the bulb electrical conductors from the filament emerge from the opening in the bulb, placing an exhaust tube partially inside the bulb through the opening, the conductors passing between the exhaust tube and the bulb, disposing a tungsten needle inside said exhaust tube at least to the level of the joint between said exhaust tube and said bulb while heat sealing the exhaust tube to the bulb, subjecting the interior of the bulb to a vacuum, hermetically sealing the exhaust tube and threading the cap over the exhaust tube for connection to the sealed joint between the exhaust tube and the bulb, the cap having two electrical contacts for electrical connection to the conductors. 